The present invention is particularly, but not exclusively, useful for x-ray examination of large objects. The fuselage and wings of aircraft, boat hulls, submarine bulkheads, pressure vessels, fuel tanks and pipelines are examples of objects that may require x-ray inspection to detect internal structural flaws or for other reasons. Prior x-ray systems and procedures are not ideally adapted for radiographic examination of such structures.
In one prior process for x-raying large objects, a point source of x-rays is situated at successive locations along the object in order to expose x-ray film which may be at the other side of the object or within the object. This is an undesirably slow procedure as the film must be removed and developed in order to obtain the desired information. In some cases, an impractically large amount of film may be required.
Another prior process for x-ray inspection of large objects avoids this problem and provides a real time or instantaneous image by replacing the film with an image intensifier type of x-ray detector. Systems of this kind require a precise alignment of the x-ray source and the detector. In some cases the source and detector are secured to a stationary support which holds the two components in the required positions relative to each other while the object undergoing examination travels between them. In other instances, the source and detector are secured to opposite ends of an arm which holds the two components in the required precise alignment while enabling joint movement of the source and detector along the object. The arm typically has a C-shaped configuration in order to reach around the object.
The requirement that the object be traveled between a stationary source and stationary detector or, alternately, that the source and detector be interconnected by a rigid structure makes it impractical or complicated and expensive at best to x-ray many large objects with systems of this kind. Manipulating large objects, such as an aircraft for example, between a stationary source and detector in the necessary manner is not a practical procedure. A C-arm interconnection between the source and detector of sufficient size to enable joint movement of a precisely aligned source and detector along the aircraft would be extremely bulky and costly and difficult to maneuver. In addition, the protruding wings and empennage of the aircraft would restrict the positioning of the apparatus relative to the aircraft.
Considering another example, a lengthy pipe of reasonably small diameter can be x-rayed by a source and imaging detector of the above described kind but the source and detector must be at opposite sides of the pipe as the need for a rigid interconnection between the two components makes it difficult or impossible to situate one component within the pipe. Consequently, internal characteristics of opposite sidewall regions of the pipe are superimposed in the resulting x-ray images and this complicates interpretation of the data.
Thus a system which does not require precise alignment of the x-ray source and x-ray detector and/or a rigid structural interconnection between the two components would be highly advantageous. The size and configuration of the object to be examined would not impose practical restrictions of the above discussed kind on the usages of such a system.
Prior systems of the above discussed kind for x-ray inspection of large objects that are designed to provide high resolution in the images have an undesirably small field of view. The field of view is determined by the size of the detector rather than the size of the x-ray source. The best resolution is obtained by using an array of minute detectors such as charge coupled devices, use of geometric magnification with image intensifiers or x-ray sensitive video cameras. All of these devices have a relatively small field of view. This slows the inspection process as the throughput of image data is a function of the field of view. It would be advantageous if the speed of examination were not determined by detector size.
X-ray examination of objects can be facilitated and made more informative if the x-ray system views the examined object from different angles and provides images corresponding to different viewing angles. Use of the above described prior x-ray imaging systems for this purpose is undesirably complicated as the x-ray source and x-ray detector must be linked by rigid alignment structure and be jointly shifted to different positions or the object itself must be maneuvered into a series of different orientations to obtain a sequence of images taken at different angles.
The present invention is directed to overcoming one or more of the problems discussed above.